Utica Dunkirk E42 Error Code

What does Utica Dunkirk E42 mean?

E42 on the Dunkirk DMG-240 indicates that the onboard low water pressure sensor has detected system pressure below the minimum required threshold, or that the sensor wiring is disconnected. This code refers specifically to the factory-installed low water pressure switch inside the boiler, not any field-installed external low-water cutoff device. The boiler locks out to prevent dry-firing.

Symptoms

• E42 displayed on the DMG-240 control panel — boiler is locked out.
• Tridicator or system pressure gauge shows pressure below 15 psi.
• System may have a visible water leak at fittings, relief valve, or expansion tank connection.
• Boiler will not start even after power cycling until pressure is restored.

Common causes

• System water pressure has dropped below the minimum threshold due to a leak or expansion tank failure.
• Wiring harness to the onboard low water pressure sensor is loose or disconnected.
• Low water pressure sensor not securely installed on the boiler block.
• Onboard pressure sensor has failed.

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Diagnostic steps

1. Check system water pressure

   Read the system pressure on the tridicator gauge. If pressure is below 15 psi, add water through the fill valve until pressure reaches 15–20 psi.

2. Inspect the system for leaks

   Check all visible piping, fittings, air vents, the relief valve discharge, and the expansion tank connection for evidence of water leakage. Repair any leak found before refilling.

3. Verify the pressure sensor wiring

   Locate the onboard low water pressure sensor (item 12 in the wiring diagram). Inspect the wiring harness connector and reseat it securely on the sensor terminals.

4. Confirm sensor installation

   Check that the low water pressure sensor is fully threaded into the boiler block and is not loose. A loose sensor can cause intermittent or false E42 faults.

5. Replace the sensor if fault persists

   If system pressure is correct and wiring is secure but E42 remains, replace the onboard low water pressure sensor with the manufacturer-approved replacement part.

When to call a professional

Call a licensed technician if the system pressure cannot be restored to 15 psi or if leaks are found in the boiler's internal piping or heat exchanger. Pressure sensor replacement and diagnosis of persistent low-pressure conditions due to expansion tank sizing or relief valve failure require a qualified plumbing and heating technician.